http_response_code is basically a shorthand way of writing a http status header, with the added bonus that PHP will work out a suitable Reason Phrase to provide by matching your response code to one of the values in an enumeration it maintains within php-src/main/http_status_codes.h. Note that this means your response code must match a response code that PHP knows about. You can't create your own response codes using this method, however you can using the header method.

In summary - The differences between "http_response_code" and "header" for setting response codes:

1. Using http_response_code will cause PHP to match and apply a Reason Phrase from a list of Reason Phrases that are hard-coded into the PHP source code.

2. Because of point 1 above, if you use http_response_code you must set a code that PHP knows about. You can't set your own custom code, however you can set a custom code (and Reason Phrase) if you use the header method.

@craig at craigfrancis dot co dot uk@ wrote the function that replaces the original. It is very usefull, but has a bug. The original http_response_code always returns the previous or current code, not the code you are setting now. Here is my fixed version. I also use $GLOBALS to store the current code, but trigger_error() instead of exit. So now, how the function will behave in the case of error lies on the error handler. Or you can change it back to exit().